This invention relates to circuit interrupters, and more specifically relates to a novel arc runner construction for the arc runner of an arc spinner type of circuit interrupter.
Arc spinner type interrupters are known in the art and are typically shown in U.S. Pat. No. 4,052,577, in the name of Gerald A. Votta, as well as U.S. Pat. No. 4,052,576, in the name of Robert Kirkland Smith.
In these devices, a flat conductive ring, hereinafter called the arc runner, is provided which is disposed in a plane perpendicular to the axis of the interrupter and perpendicular to the flow of arc current during circuit interruption. This arc runner is then electrically connected in series with a coil to which it is closely coupled. A movable contact is then arranged to make annular contact engagement and disengagement with a cooperating annular surface of the arc runner facing away from the coil. When the contact opens, an arc is drawn from the arc runner to the movable contact and the arc current flows through the coil. This then induces a circulating current in the arc runner, which is a shorted turn, and both the arc runner and coil then produce a resultant magnetic field in the region of the arc.
The magnetic field component from the arc runner circulating current is displaced in phase from that of the coil so that a fairly substantial field is present just before a current zero interval. The effect of the arc current in the magnetic field produced by the arc runner and coil is such that a Lorentz force is established which tends to rotate the arc around the arc runner. This rotational movement of the arc is through a relatively static dielectric gas which fills the arc space and thereby tends to deionize and cool the arc so that the arc can be interrupted at the first current zero.
A problem exists in such interrupters when low currents (below about 3000 amperes) with high transient recovery voltage (TRV) frequencies of about 20 k Hz. Thus, in this low current range, the arc is interrupted in a plain break mode and not in a rotating arc mode. Standard arc-resistant materials, such as copper tungsten alloys, perform well in the plain break mode, but they do not work well in the rotating arc mode. Standard electrolytic copper performs very well in the rotating mode, but does not work well in the plain break condition. Therefore, in the past, it has been necessary to provide auxiliary means, such as a puffer assist, to allow the use of electrolytic copper for the rotating arc mode while giving the interrupter low current, high frequency TRV interruption capability.